JP6816162B6 - How to produce prenol and plenal from isoprenol - Google Patents

Description

The present invention relates to a method for preparing 3-methyl-2-butenol (prenol) and 3-methyl-2-butenal (prenol) from 3-methyl-3-butenol (isoprenol). This method can be performed continuously or in batch.

3-Methyl-2-butenol (prenol) and 3-methyl-2-butenal (prenol) are important materials of value as they are used on an industrial scale as synthetic units in many preparation processes. For example, they are particularly suitable as starting materials for preparing isoprenoid compounds. For example, prenol and plenal are used, among other things, to prepare odorants, such as citral, or vitamins, such as vitamin E and vitamin A.

Prior art discloses various methods of preparing prenol or plenal.

WO2008 / 037693 describes a multi-step method for preparing citral, in which prenol is 3-methyl-3-butenol (3-methyl-3-butenol in the presence of hydrogen and plenal, among other things, on heterogeneous noble metal catalysts). It is obtained by isomerization of isoprenol), which involves oxidative dehydrogenation of isoprenol in the gas phase and basic isomerization downstream. Specifically, the heterogeneous noble metal catalyst used in the method of preparing prenol is a Pd-containing catalyst on a ceramic carrier further containing selenium, thereby converting 55% relative to the isoprenol used. By rate, prenol is obtained with a selectivity of 91%. Plenal is derived via oxidative dehydrogenation at a temperature of 450 ° C. on a supported silver catalyst in the presence of an oxygen-containing gas, thereby converting 62.8% relative to the isoprenol used. So, you can get plenal with a selectivity of 75.6%. The described method has the disadvantage that isoamyl alcohol is formed by the isomerization of isoprenol, which cannot be easily separated from the reaction mixture. Moreover, oxidative dehydrogenation in the gas phase used to prepare plenal is inconvenient and expensive, and the high reaction temperature results in inadequate selectivity.

WO2009 / 106622 describes how the isomerization of olefinically unsaturated alcohols proceeds under fairly mild conditions by performing on a carbon-supported noble metal catalyst in an oxygen-containing atmosphere. Despite mild conditions, the isomerization of olefinically unsaturated alcohols proceeds with good yields and selectivity, which allows the formation of by-products, especially the corresponding saturated alcohols, to be kept at low levels. Means. Specifically described is 3-methyl-3 under air and high pressure at a temperature of 80 ° C. in the presence of a carbon-supported Pd catalyst on charcoal. -Partial isomerization of butenol (isoprenol) to 3-methyl-2-butenol (prenol), which is also a small proportion of 3-methyl-2-butenal (prenol), as well as a mixture of isoprenol and prenol. ) Is also formed.

A method for preparing an olefin-based unsaturated carbonyl compound by oxidative dehydrogenation of an unsaturated alcohol, wherein the oxidative dehydrogenation is carried out in a liquid phase under relatively mild conditions, for example, ACS Catal. 2011. , 1, 636-640; Catalysis Communications 2009, 10 (11), 1542; Journal of Catalysis 2008, 258 (2) and 315; Green Chemistry 2009, 11 (1), 109. In these methods, palladium catalysts are used in particular.

The prior art also describes the use of various ruthenium catalysts capable of oxidizing allyl alcohol under relatively mild conditions. For example, Larock and Veraprat in J. Org. Chem. 1984, 49, 3435-3436 prepared unsaturated aldehydes, including plenal, in the corresponding allyl alcohols in 1,2-dichloroethane at 70 ° C. in, describes the presence of 10% by weight of RuO ₂ hydrate and oxygen, as well as the preparation by oxidizing in the presence of an antioxidant 2,6-di -tert- butyl -p- cresol.

Prior art also states that prenol can be oxidized to plenal much more easily than isoprenol in known oxidative dehydrogenation methods. For example, Parlett et al., ACS Catal. 2011, 1, 636-640 described allyl alcohol in the presence of various mesoporous silicon dioxide-supported Pd catalysts (Pd mesoporous silicon dioxide catalysts) and air oxygen. , Describes a method of oxidative dehydrogenation under mild conditions. They succeeded in oxidizing the prenol, among other things, in toluene at 90 ° C. in the presence of 0.5 wt% Pd mesoporous SiO ₂ catalyst, thereby 90 at a conversion rate of 27% after 24 hours. A prenol was obtained with a selectivity of%. In contrast, isoprenol was found to be non-reactive under these reaction conditions.

WO2009 / 106621 is a gold catalyst (gold basic carrier catalyst) on which an unsaturated alcohol is supported on a basic carrier at a temperature in the range of 50 to 240 ° C. in an oxygen-containing atmosphere (in some cases, an additional precious metal like gold). A method for preparing an olefin-based unsaturated carbonyl compound by oxidative dehydrogenation in the presence of (including) is described. Specifically described is the preparation of 3-methyl-2-butenal (prenal) from 3-methyl-3-butenol (isoprenol), in which by using a basic carrier material. , 3-Methyl-2-butenal (prenal) is preferentially formed and 3-methyl-3-butenal (isoprenol) is not formed, so that no isomerization needs to be performed downstream. In addition, WO2009 / 106621 teaches that the isoprenol / prenol mixture can be used as a starting material for oxidative dehydrogenation to increase the conversion rate. However, this method uses a diluent, such as xylene, which reduces its appeal to industrial methods.

WO2008 / 037693 WO2009 / 106622 WO2009 / 106621

Parlett et al., ACS Catal. 2011, 1, 636-640 Catalysis Communications 2009, 10 (11), 1542 Journal of Catalysis 2008, 258 (2) and 315 Green Chemistry 2009, 11 (1), 109 Larock and Veraprath, J. Org. Chem. 1984, 49, 3435-3436

Therefore, there is a need for an improved method of producing prenol and prenol from isoprenol, thereby overcoming the above disadvantages resulting from the low reactivity of isoprenol with respect to oxidative dehydrogenation. Exists.

Therefore, the object of the present invention is particularly low under mild reaction conditions from 3-methyl-2-butenol (prenol) and 3-methyl-2-butenal (prenol) to 3-methyl-3-butenol (isoprenol). It is a method that makes it possible to prepare at a reaction temperature, and is to provide a method that can achieve a high conversion ratio despite the low reaction rate of isoprenol for oxidative dehydrogenation. 3-Methyl-2-butenol (prenol) and 3-methyl-2-butenal (prenol) should be obtained in the form of a composition containing prenol and plenal in approximately equal molar amounts. Moreover, the method should allow the preparation of prenol and plenal with high total selectivity and should minimize the formation of by-products that are difficult to remove. The method should, in addition, be suitable for continuous processing methods.

This purpose is surprisingly
i) 3-Methyl-3-butenol is subjected to catalytic isomerization on a carbon-supported Pd catalyst in the presence of a gaseous mixture containing 1% to 15% by volume of oxygen to produce the first product mixture. At least 40% by volume 3-methyl-2-butenol, at least 5% by weight 3-methyl-3-butenol, and 0% to 15% by weight 3-methyl-2-butenal based on total weight. Obtaining the first product mixture containing,
ii) The first product mixture obtained in step i) is 5% by volume to 25% by volume on a Pd catalyst containing SiO ₂ and / or Al ₂ O ₃ as a carrier material or on a carbon-supported Pd / Au catalyst. Performed oxidative dehydrogenation in the presence of a gaseous mixture containing% by volume, 3-methyl-2-butenal is enriched and 3-methyl-2-butenol is depleted compared to the first product mixture. A (deplete) second product mixture was obtained, where the molar ratio of 3-methyl-2-butenol to 3-methyl-2-butenal in the second product mixture was 75:25 to 35:65. Is within the range of
It is realized by the method of preparing a composition containing 3-methyl-2-butenol and 3-methyl-2-butenal.

It has been found that the reaction product from the catalytic isomerization of isoprenol can advantageously be used for direct oxidative dehydrogenation without intermediate purification, optionally after removal of the catalyst. The reaction rate, or conversion rate, of the isomerized products used for oxidative dehydrogenation is in this case comparable to the use of pure prenol, and even higher overall prenol and prenol selectivity is achieved. To.

In addition, it has been found that the reaction rate and selectivity in oxidative dehydrogenation can be further increased by adding a base.

Therefore, the present invention further provides a method as defined above, wherein the oxidative dehydrogenation in step ii) is further carried out in the presence of a base.

The present invention further relates to the continuous implementation of the methods as defined above and below.

The method of the invention has at least one of the following advantages:
--This method makes it possible to prepare prenol and plenal with a high total selectivity.
--The method of the present invention can achieve high conversion ratios even under mild reaction conditions, which largely avoids or completely avoids the formation of by-products that are difficult to remove. It means that even it is possible.
--By the method of the present invention, a composition containing prenol and plenal in similar molar amounts can be obtained.
--Since this method does not require particularly complicated intermediate purification, it is easy to carry out even though it is a two-step reaction method.
--This method can significantly or completely eliminate the use of external diluents, which results in higher conversion rates and significantly improved airtime yields.
--This method can be carried out continuously, which is advantageous.
-Due to the features described above, the methods of the present invention are suitable for the industrial scale preparation of prenol and plenal, in addition, the favorable economic feasibility is noteworthy.

Step i):
In step i) of the method of the invention, 3-methyl-3-butenol (isoprenol) is isomerized to 3-methyl-2-butenol (prenol). According to the present invention, the isomerization is carried out on a carbon-supported Pd catalyst in the presence of a gas mixture containing 1% to 15% by volume of oxygen.

The contact isomerization can be carried out either in the liquid phase or in the gas phase, and the contact isomerization is preferably carried out in the liquid phase.

Contact isomerization is typically carried out in the presence of a gaseous mixture containing 1% to 15% by volume of oxygen, i.e. in the presence of an oxygen-containing atmosphere. A gaseous mixture containing 1% to 15% by volume of oxygen is placed in the reaction zone, for example, by a single injection before or at the start of the reaction, by repeated injections during the reaction, or by continuous introduction over the entire course of the reaction. Can be supplied. Preferably, in step ii) of the method of the invention, the oxygen-containing gaseous mixture is fed into the reaction zone by continuous introduction over the entire course of the reaction.

Typically, the gas mixture used in step i) of the method of the invention is in the range of 1% to 15% by volume, preferably 2% to 12% by volume, especially 3% to 10% by volume. Includes oxygen content of.

In a particularly preferred embodiment of step i) of the method of the invention, the oxygen-containing atmosphere is exchanged by supplying an oxygen-enriched gas mixture and removing the oxygen consumable gas mixture. The oxygen enrichment and the supply and removal of the oxygen consumable gas mixture can be carried out sequentially or simultaneously. Preferably, the exchange of the oxygen-containing atmosphere is repeated and the total amount of the oxygen-containing gas mixture exchanged corresponds to at least the volume of the amount of gas present in the reaction zone. More preferably, the total amount of the oxygen-containing gas mixture exchanged corresponds to a volume several times, for example ten times, the volume of the gas present in the reaction zone. The exchange can be carried out stepwise or continuously. Preferably, the oxygen-containing atmosphere is continuously exchanged.

When the oxygen-containing atmosphere is continuously exchanged, the exchange rate of the oxygen-containing gaseous mixture in catalytic isomerization is typically in the range of 1-200 L / hour, especially relative to 100 g of isoprenol used. It is in the range of 3 to 120 L / hour, especially in the range of 5 to 80 L / hour.

Upon completion of the catalytic isomerization in step i), not only 3-methyl-2-butenol (prenol), but also 3-methyl-3-butenol (isoprenol) and optionally a small amount of 3-methyl-2-butenal (prenol). A first product mixture containing both) is obtained.

In general, the first product mixture obtained in step i) of the method of the invention is at least 40% by weight 3-methyl-2-butenol, at least 5% by weight 3-methyl-3-butenol, and 0% by weight. Contains% to 15% by weight 3-methyl-2-butenal.

Preferably, the first product mixture obtained in step i) comprises 40% to 80% by weight, more preferably 45% to 70% by weight of 3-methyl-2-butenol.

Preferably, the first product mixture obtained in step i) comprises 0% to 15% by weight, more preferably 5% to 10% by weight of 3-methyl-2-butenal.

Preferably, the first product mixture obtained in step i) comprises 5% to 59% by weight, more preferably 20% to 50% by weight of 3-methyl-3-butenol.

In a preferred embodiment of the method of the invention, the first product mixture obtained in step i) is
i.1 40% to 80% by weight 3-methyl-2-butenol,
i.20 0% to 15% by weight 3-methyl-2-butenal,
i.3 5% to 59% by weight 3-methyl-3-butenol, and
i.40 Consists of 0% to 10% by weight compounds other than i.1, i.2, and i.3.

In a particularly preferred embodiment of the method of the invention, the first product mixture obtained in step i) is
i.1 45% to 70% by weight 3-methyl-2-butenol,
i.2 5% to 10% by weight 3-methyl-2-butenal,
i.3 20% to 50% by weight 3-methyl-3-butenol, as well as
i.40 Consists of 0% to 5% by weight compounds other than i.1, i.2, and i.3.

The total proportion of 3-methyl-2-butenol, 3-methyl-2-butenal, and 3-methyl-3-butenol in the first product mixture is based on the total weight of the first product mixture. It is typically at least 80% by weight, preferably at least 85% by weight, more preferably at least 90% by weight or more, for example at least 92% by weight.

According to the present invention, the isomerization in step i) occurs in the presence of a carbon-supported Pd catalyst, i.e. a Pd catalyst containing carbon (C), eg, an activated carbon-based carrier material. .. Various types of charcoal or various types of graphite, as known to those of skill in the art and described in the literature, are simply examples of such materials.

Suitable carbon-based carrier materials are, in principle, all carbon materials known to those of skill in the art for such use. The carrier material may preferably be used in the form of moldings, granules, strands, pellets, spalls, tablets, or prills. BET surface area of the support material (25 ° C.) typically, 1~10000m ² / g, but preferably in the range of 10~5000m ² / g, not critical in most of the methods of the present invention ..

The Pd content of the carbon-supported Pd catalyst used for catalytic isomerization is typically in the range of 0.1% to 20% by weight, based on the total weight of the carbon-supported Pd catalyst. It is preferably in the range of 0.5% by weight to 15% by weight, particularly in the range of 1% by weight to 10% by weight.

Typically, the amount of carbon-supported Pd catalyst used for catalytic isomerization is in the range of 0.1% to 20% by weight, preferably in the range of 0.1% to 20% by weight, based on the amount of isoprenol present in the reaction mixture. It is in the range of 0.2% by weight to 10% by weight, more preferably in the range of 0.5% by weight to 5% by weight.

Contact isomerization is typically performed at pressures in the range of 1-100 bar, preferably in the range of 1-50 bar, especially in the range of 2-20 bar.

Typically, the reaction temperature for contact isomerization is in the range of 20-150 ° C, preferably in the range of 40-120 ° C, especially in the range of 50-110 ° C.

Contact isomerization can be carried out in the presence or absence of an external solvent.

If the catalytic isomerization is carried out in the presence of an external solvent, this is typically an inert organic solvent. In the context of the present invention, the Inactive solvent is understood to mean a solvent that, under selected reaction conditions, does not participate in any reaction with the compounds and materials involved in the isomerization.

Suitable inert solvents are, for example, aliphatic hydrocarbons such as pentane, hexane, heptane, ligroin, petroleum ether, or cyclohexane, halogenated hydrocarbons such as dichloromethane, trichloromethane, tetrachloromethane, aromatic hydrocarbons such as Benzene, toluene, xylene, halogenated aromatic hydrocarbons such as chlorobenzene, dichlorobenzene, ethers such as diethyl ether, methyl tert-butyl ether, dibutyl ether, diphenyl ether, tetrahydrofuran, or 1,4-dioxane, and mixtures thereof. .. Particularly suitable examples are toluene, o-xylene, p-xylene, tetrahydrofuran, 1,4-dioxane, or diphenyl ether.

It is preferable to carry out catalytic isomerization without the addition of an external solvent.

Contact isomerization can be performed in either batch or continuous mode. It is preferable to carry out contact isomerization in continuous mode.

Typically, the catalytic isomerization of 3-methyl-3-butenol to 3-methyl-2-butenol has a conversion rate of 30% to 80% relative to the 3-methyl-3-butenol used. Up to, preferably up to 35% to 75% conversion rates, especially up to 40% to 70% conversion rates.

The 3-methyl-3-butenol used for catalytic isomerization is typically obtained as a waste stream in the recovery of commercially available 3-methyl-3-butenol, or valuable materials, eg in the recovery of citral. 3-Methyl-3-butenol, and mixtures thereof. Commercially available 3-methyl-3-butenol is a cheap and readily available chemical starting material that can be synthesized on an industrial scale, for example from formaldehyde and isobutylene.

The first product mixture obtained in step i) of the method of the present invention is hereinafter also referred to as "product from catalytic isomerization". The first product mixture obtained in step i) of the method of the invention is typically after removal of the catalyst, optionally after further purification, eg, distillation purification, or optionally after removal of the catalyst. It is used for oxidative dehydrogenation in step ii) without any further purification, or is fed in step ii) in continuous mode.

Preferably, the product from catalytic isomerization is used for oxidative dehydrogenation in step ii), optionally after removal of the catalyst, without further purification, or in continuous mode step ii). Is supplied to.

Step ii):
Oxidative dehydrogenation in step ii) of the method of the present invention is generally carried out in the presence of a Pd catalyst containing SiO ₂ , Al ₂ O ₃ , or a mixture of SiO ₂ and Al ₂ O ₃ as a carrier material. Alternatively, it is carried out in the presence of a Pd / Au catalyst supported on carbon.

Preferably, the Pd catalyst used for oxidative dehydrogenation is a Pd catalyst supported on SiO ₂ or SiO ₂ / Al ₂ O ₃ , in particular a Pd catalyst supported on SiO ₂ / Al ₂ O ₃ .

Preferably, the carbon-supported Pd / Au catalyst used for oxidative dehydrogenation is a Pd / Au catalyst containing a carrier material based on carbon (C), eg activated carbon. For activated carbon suitable as a carrier material for this purpose, see the description above for carbon-supported Pd catalysts.

The metal content of the Pd catalyst and / or the Pd / Au catalyst used in step ii) of the method of the present invention is not particularly limited. Preferably, the metal content of the Pd catalyst or Pd / Au catalyst used in step ii) of the method of the present invention is in the range of 0.1% by weight to 25% by weight, preferably in the range of 0.5% by weight to 15% by weight. Of these, in particular, it is in the range of 2% by weight to 10% by weight.

The Pd content of the Pd / Au catalyst used in step ii) of the method of the present invention is typically 0.5% to 15% by weight based on the total weight of the Pd / Au catalyst carried on carbon. It is preferably in the range of 1% by weight to 10% by weight, particularly in the range of 2% by weight to 7% by weight.

The Au content of the Pd / Au catalyst used in step ii) of the method of the present invention is typically 0.1% to 10% by weight based on the total weight of the Pd / Au catalyst carried on carbon. It is preferably in the range of 0.5% by weight to 7% by weight, particularly in the range of 1% by weight to 5% by weight.

The weight ratio of Pd to Au in the Pd / Au catalyst used in step ii) is typically in the range of 1:50 to 3: 1, preferably in the range of 1:20 to 2: 1. Especially in the range of 1:10 to 1.2: 1.

Pd catalysts supported on SiO ₂ , Al ₂ O ₃ , or SiO ₂ / Al ₂ O ₃ used by the present invention, or Pd / Au catalysts supported on carbon used by the present invention are available to those skilled in the art. It can be prepared by a known method described in the literature.

Typically, the amount of Pd or Pd / Au catalyst used for oxidative dehydrogenation is 0.1% to 20% by weight based on the total weight of the reaction mixture for oxidative dehydrogenation. It is in the range of 0.2% by weight to 10% by weight, more preferably in the range of 0.4% by weight to 5% by weight.

Oxidative dehydrogenation in step ii) of the method of the present invention is preferably carried out in the presence of a Pd catalyst comprising SiO ₂ , Al ₂ O ₃ , or a mixture of SiO ₂ and Al ₂ O ₃ as a carrier material. Will be done.

Therefore, a preferred embodiment of the present invention relates to a method as defined above, wherein in step ii) a Pd catalyst containing SiO ₂ and / or Al ₂ O ₃ as a carrier material is used as a catalyst.

See the description above for preferred and particularly preferred Pd content and / or carrier materials used in step ii) of this embodiment, and preferred and particularly preferred amounts of Pd catalyst used.

Oxidative dehydrogenation is typically carried out in the liquid phase, which means that the pressure and temperature for conversion are selected so that the feed material is in liquid form.

The temperature in oxidative dehydrogenation is preferably in the range of 10 to 150 ° C, more preferably in the range of 20 to 130 ° C, especially in the range of 40 to 120 ° C.

Oxidative dehydrogenation can be carried out at ambient pressure, reduced pressure or high pressure. It is preferable to carry out oxidative dehydrogenation at high pressure. Particularly preferred is oxidative dehydrogenation performed at pressures in the range of 1-200 bar, more preferably 1.5-100 bar, especially 2-50 bar.

Oxidative dehydrogenation is typically carried out in the presence of a gaseous mixture containing 5% to 25% by volume of oxygen, i.e. in the presence of an oxygen-containing atmosphere.

The gaseous mixture used in step ii) of the method of the invention, containing 5% to 25% by volume of oxygen, can be prepared, for example, by a single injection before or at the beginning of the reaction, or by repeated injections during the reaction. Alternatively, it can be supplied to the reaction zone by continuous introduction over the entire process of the reaction. Preferably, in step ii) of the method of the invention, the oxygen-containing gaseous mixture is fed into the reaction zone by continuous introduction over the entire course of the reaction.

Typically, the gas mixture used in step ii) of the method of the invention is in the range of 5% to 25% by volume, preferably 7% to 20% by volume, especially 8% to 15% by volume. Includes oxygen content of.

In a particularly preferred embodiment of step ii) of the method of the invention, the oxygen-containing atmosphere is exchanged by supplying an oxygen-enriched gas mixture and removing the oxygen-depleting gas mixture. The oxygen enrichment and the supply and removal of the oxygen consumable gas mixture can be carried out sequentially or simultaneously. Preferably, the exchange of the oxygen-containing atmosphere is repeated and the total amount of the oxygen-containing gas mixture exchanged corresponds to at least the volume of the amount of gas present in the reaction zone. More preferably, the total amount of the oxygen-containing gas mixture exchanged corresponds to a volume several times, for example ten times, the volume of the gas present in the reaction zone. The exchange can be carried out stepwise or continuously. Preferably, the oxygen-containing atmosphere is continuously exchanged.

When the oxygen-containing atmosphere is continuously exchanged, the exchange rate of the oxygen-containing gas or gas mixture in oxidative dehydrogenation is typically relative to 100 g of the first product mixture used in step ii). Is in the range of 1 to 200 L / hour, preferably in the range of 3 to 120 L / hour, especially in the range of 5 to 80 L / hour.

Oxidative dehydrogenation can be carried out in the presence or absence of the added organic solvent.

If oxidative dehydrogenation is carried out in the presence of the added organic solvent, this is preferably with the organic solvent which is inert under the reaction conditions, as already defined for contact isomerization. is there.

It is preferable that no external organic solvent is added to the oxidative dehydrogenation.

After oxidative dehydrogenation in step ii) of the method of the invention is complete, 3-methyl-2-butenal is enriched as compared to the first product mixture from step i), 3-methyl-2. -A second product mixture depleted of butenol is generally obtained.

Increasing at least one of the reaction parameters, in particular the reaction temperature, pressure, reaction time, or residence time, or the amount of catalyst used, generally increases the conversion rate or the reaction mixture of oxidative dehydrogenation ( The content of 3-methyl-2-butenal in the second product mixture) is increased. However, loss of selectivity is expected due to degradation reactions and further reactions. In particular, if the reaction time or residence time is lengthened, side reactions such as peroxidation may increase (increased formation of acids, epoxides, dislocation products, etc.). More specifically, this can result in increased formation of isoamyl alcohol, which cannot be easily separated from the reaction mixture.

For this reason, the reaction parameters in oxidative dehydrogenation, in particular the amount of catalyst, pressure, reaction temperature, and reaction time or residence time, are generally the proportion of 3-methyl-2-butenal in the second product mixture. However, typically in the range of 2% to 55% by weight, preferably in the range of 10% to 45% by weight, especially 15% to 35% by weight, based on the total weight of the second product mixture. Selected to be in the% range.

Oxidative dehydrogenation in step ii) of the method of the invention typically has a molar ratio of 3-methyl-2-butenol to 3-methyl-2-butenal in the second product mixture of 75 :. It is carried out in the range of 25 to 35:65, preferably in the range of 70:30 to 40:60, especially in the range of 65:35 to 45:55.

In the second product mixture thus obtained, after removing the Pd catalyst used subsequently, and at least a part of 3-methyl-3-butenol present in the second product mixture was removed by distillation. Later, it can be used directly as a feed material for preparing valuable isoprenoid materials, such as fragrances, such as citral, or vitamins, such as vitamin E and vitamin A.

In a preferred embodiment of the method of the invention, the oxidative dehydrogenation in step ii) is further carried out in the presence of a base. Suitable bases that can be used for oxidative dehydrogenation are mineral bases, especially hydroxides of alkali metals and alkaline earth metals, such as LiOH, NaOH, KOH, RbOH, CsOH, Mg ( OH) ₂ or Ca (OH) ₂ . More preferably, the base used for oxidative dehydrogenation is selected from NaOH and KOH.

The proportion of bases in the reaction mixture is in the range of 0.01% to 2% by weight, more preferably 0.05% to 1.5% by weight, based on the amount of the first product mixture used in step ii). Within the range, especially within the range of 0.1% to 1% by weight.

In a particular embodiment of the method of the invention, oxidative dehydrogenation of the first product mixture obtained in step i), as defined above, is carried out on SiO ₂ / Al ₂ O ₃ Pd. From 0.1% by weight based on the amount of the first product mixture used, in the presence of a gaseous mixture containing 8% to 15% by volume oxygen, on the catalyst or on a carbon-supported Pd / Au catalyst. 70: 3-methyl-2-butenol and 3-methyl-2-butenal at temperatures in the range of 40-120 ° C and pressures in the range of 2-50 bar in the presence of 1% by weight KOH or NaOH. It is carried out to obtain a second product mixture containing in a molar ratio in the range of 30-40:60.

In a particularly preferred embodiment of steps i) and ii) of the method of the invention, the oxygen content of the gas mixture used in step i) is 2% by volume from the oxygen content of the gas mixture used in step ii). ~ 10% by volume, preferably 3% to 8% by volume, especially 4% to 6% by volume lower.

In a more particularly preferred embodiment of the method of the invention, in steps i) and ii), the oxygen-enriched gas mixture is continuously supplied to the respective reaction regions and the oxygen depleting reaction mixture is continuously removed. The continuous supply of the oxygen-enriched gas mixture to each reaction zone can be carried out in various ways. It is preferable to continuously supply the oxygen-enriched gas mixture below the liquid surface of each reaction mixture.

In a particular embodiment of the method of the invention, in steps i) and ii), the oxygen-enriched gas mixture is continuously fed to the respective reaction regions and the oxygen depleting reaction mixture is continuously removed, wherein the oxygen-enriched gas mixture is continuously removed. The oxygen-enriched gas mixture is fed below the liquid surface of each reaction mixture.

Distillation Separation In a further embodiment of the method of the invention, the second product mixture obtained in step ii) was subjected to distillation separation to enrich 3-methyl-2-butenol and 3-methyl-2-butenal. The product fraction and the reaction fraction enriched with 3-methyl-3-butenol are used.

The equipment suitable for the distillation separation of the second product mixture obtained in step ii) is all the equipment for the distillation separation of the reaction mixture containing the liquid component. Suitable equipment include distillation columns, such as tray columns (bubble-cap trays, sieve plates, sieve trays, structured packing). ) Or with a random packing) or a spinning band column, an evaporator such as a thin film evaporator, a falling film evaporator. ), Forced circulation evaporator, Sambay evaporator, and combinations thereof. Particularly preferred is to carry out the distillation separation of the composition obtained in step ii) using a distillation column and / or a rotating band column, particularly a rotating band column.

In distillation separation, the vapor is first extracted from the second product mixture obtained in step ii) and then at least partially condensed. The vapor condensation or partial condensation can be carried out using any suitable condenser. These can be cooled with any desired cooling medium. A condenser having air cooling and / or water cooling is preferable, and air cooling is particularly preferable.

The product fraction enriched with 3-methyl-2-butenol and 3-methyl-2-butenal, obtained after distillation separation, is subsequently subjected to further purification steps (familiar to those skilled in the art) according to the desired purity. It can be subjected to customary liquid chromatography or distillation). Generally, the product fractions enriched with 3-methyl-2-butenol and 3-methyl-2-butenal, obtained after distillation separation, are used to prepare valuable isoprenoid materials, for example, in flavoring agents. It can be used directly to prepare, for example, citral, or vitamins, such as vitamin E and vitamin A.

The 3-methyl-3-butenol-enriched reactant fraction obtained after distillation separation can be used as a feedstock for catalytic isomerization in step i). To this end, a new, or pure, commercially available 3-methyl-3-butenol, is optionally added to this fraction enriched with 3-methyl-3-butenol. If catalytic isomerization is continuous, new 3-methyl-3-butenol is generally added to the 3-methyl-3-butenol-enriched reactant fraction used in step i). In that case, the amount of new 3-methyl-3-butenol added is typically the contact isomerization of the new 3-methyl-3-butenol followed by oxidative dehydrogenation in step ii). Corresponds to the amount expected to be converted in.

Continuous Execution The method of the present invention can be executed in batch or continuous mode. Preferably, at least one of steps i) and ii) of the method of the invention is performed continuously. In a particularly preferred embodiment of the method of the invention, both steps i) and ii) are performed sequentially.

The spatiotemporal velocity of the catalyst in oxidative dehydrogenation is typically in the range of 0.1-50 kg of 1 kg of catalyst and 3-methyl-2-butenal per hour, preferably 1 kg of catalyst and 3-methyl- per hour. 2-butenal 0.2-30 kg, especially in the range of 1 kg catalyst and 3-methyl-2-butenal 0.5-15 kg per hour.

In continuous mode, the method of the invention can be performed with one or more reactors. It is preferred to perform the method with at least two reactors connected to each other in the form of a cascade.

When the two method steps are performed sequentially, catalytic isomerization and oxidative dehydrogenation are performed in parallel, but each is spatially separated from each other in at least one reactor.

For example, contact isomerization as defined above is performed in the first reactor. The first product mixture thus obtained is continuous with oxidative dehydrogenation, which optionally removes the catalyst in solid form and proceeds in parallel with catalytic isomerization in the second reactor. It is directly supplied as a generated logistics. At the same time, 3-methyl-3-butenol is continuously supplied to the first reactor as defined above in order to keep the volume of the reaction solution in the first reactor constant. A second product enriched with 3-methyl-2-butenal and depleted with 3-methyl-2-butenol compared to the first product mixture obtained after oxidative dehydrogenation in the second reactor. The product mixture is removed from the second reactor as a product stream, and after the catalyst has been removed, it can be fed to further processes as feed material, as described above.

The present invention will be described in detail with reference to Examples described below. In doing so, the examples should not be considered as limiting the invention.

In the following examples, the following abbreviations are used:

The exhaust mode represents a reaction method that involves exchanging an oxygen-containing atmosphere, that is, a reaction method that continuously introduces an oxygen-enriched (new) gas mixture and at the same time continuously removes an oxygen-depleted (used) gas mixture. ..
Exhaust represents the amount of oxygen-containing gaseous mixture exchanged.
MBE stands for isoprenol (3-methyl-3-butenol).
SAP represents a Pd catalyst supported on SiO ₂ / Al ₂ O ₃ .

[Example]
In this example, the following catalysts were used.

i) Contact isomerization:
Individual experiments were generally performed in a stable pressure reactor with a mechanical stirrer in an oxygen-containing atmosphere. Performing laboratory-scale contact isomerization, baffles, heating device (Huber Ministat 230-CC), sparging stirrer (Pt 100, 7 bar safety valve, gas connection with QC quick release coupling), A 350 mL glass pressure vessel (DN 50 for 8 bar) with a pressure reducing valve for a pressure range of 0 to 10 bar, and optionally a flowmeter at the gas inlet and a pressure regulator at the gas outlet, ie a pressure release valve. ) Was used.

Unless otherwise stated, the following standard conditions were used for the following contact isomerization experiments.
・ Stirrer speed: 1000rpm
・ Exchange rate of oxygen-containing gas: 30 L / hour ・ Reaction temperature: 80 ℃
・ Pressure in the reactor: 5 to 20 bar ・ Amount of material to be supplied: 100 g

Contact isomerization experiments were performed with various Pd catalysts. The results of the experiment are summarized in Table 1.

As is clear from Table 1, carbon-supported Pd catalysts exhibit desirable activity. In general, a total selectivity of over 90%, ie the combined selectivity of prenol and plenal, is obtained. It was possible to successfully recycle the catalyst and subsequently reuse it. In addition, in general, a decrease in the formation of isoamyl alcohol due to the reaction conditions used was observed, the value of which was in the range of 0.5 to 1.0 area%.

Table 2 shows the profile of the conversion rate of MBE over time and the amount of prenol and plenal formed in a typical contact isomerization reaction.

As can be inferred from Table 2, after a reaction time of approximately 3 hours, a maximum prenol selectivity is obtained with an MBE conversion of> 50%.

The product from the isomerization can be used for oxidative dehydrogenation without further purification. This causes differences in the composition of the reaction feeder depending on the reaction profile and reaction time.

ii) Oxidative dehydrogenation of products from catalytic isomerization:
The feedstock used in the oxidative dehydrogenation experiments below were products from catalytic isomerization performed in the same manner as in the experiments detailed in i). These isomerized products were used directly for oxidative dehydrogenation without intermediate purification after removing the catalyst.

Individual oxidative dehydrogenation experiments were generally performed in a stable pressure reactor with a mechanical stirrer in an oxygen-containing atmosphere. All experiments were performed with a higher O ₂ content (10% by volume) compared to catalytic isomerization, preferably 5% higher O ₂ content. Unless otherwise stated, the following standard conditions were used for the following oxidative dehydrogenation experiments.
・ Stirrer speed: 1000rpm
・ Exchange rate of oxygen-containing gas: 30 L / hour ・ Reaction temperature: 80 ℃
・ Pressure in the reactor: 5 to 20 bar ・ Amount of material to be supplied: 100 g

Oxidative dehydrogenation experiments on isomerized products from i) include 3% Pd SAP dry-reduced (BASF-Italia) catalysts and 4% Pd / 4% Au catalysts carried on activated carbon (4% Pd / 4). % Au activated carbon) was used.

Tables 3 and 4 summarize the results from oxidative dehydrogenation experiments using products from catalytic isomerization directly. Tables 3 and 4 each list the composition of the isomerized product used at the top of the line (t = 0), where the values reported for t = 0 were used in each case. It means that it corresponds to the composition of the isomerized product. The different compositions in the isomerization product and the total proportion of MBE, prenol, and plenal could be different reaction conditions in the catalytic isomerization performed in each case, such as different residence times, catalyst recycling practices, or other. Due to the difference.

Since no catalytic toxin is clearly formed during catalytic isomerization, the products from catalytic isomerization can be used directly for oxidative dehydrogenation. Recycling experiments (up to 4 times) were successful for both the 3% Pd SAP catalyst and the 4% Pd / 4% Au catalyst used. It is even possible to observe an increase in activity here. Increasing temperature, pressure, and residence time generally increased yields, but loss of selectivity was expected due to decomposition reactions and further reactions, such as peroxidation.

iii) Oxidative dehydrogenation of a mixture of prenol and MBE and pure prenol:
Table 6 shows the results from oxidative dehydrogenation experiments on specific mixtures of prenol and MBE, and pure prenol as a comparative experiment. The values listed at t = 0 in Table 5 correspond to the amount of feed material used in each case or the composition of the feed material used in each case. 3% Pd SAP dry-reduced form (BASF-Italia) was used as the catalyst. All experiments were performed with an exhaust of 30 L / h and 0.2% NaOH. For others, the standard conditions specified in ii) were used. The total selectivity reported corresponds to the sum of the selectivity of prenol and plenal.

This experiment shows that a high total selectivity (91%) can be achieved when using a mixture of MBE / prenol (pure) for oxidative dehydrogenation. With pure prenol, in contrast, the total selectivity was only about 85%. This is consistent with findings from blank experiments showing that prenol can decompose very quickly in the presence of oxygen. Using a unique product from catalytic isomerization, results comparable to synthetic MBE / prenol mixtures are obtained. Therefore, it turns out that it is advantageous to use the MBE / prenol mixture.

Claims (17)

i) 3-Methyl-3-butenol is subjected to catalytic isomerization on a carbon-supported Pd catalyst in the presence of a gaseous mixture containing 1% to 15% by volume of oxygen to produce the first product mixture. At least 40% by volume 3-methyl-2-butenol, at least 5% by weight 3-methyl-3-butenol, and 0% to 15% by weight 3-methyl-2-butenal based on total weight. Obtaining the first product mixture containing,
ii) The first product mixture obtained in step i) is 5% by volume to 25% by volume on a Pd catalyst containing SiO ₂ and / or Al ₂ O ₃ as a carrier material or on a carbon-supported Pd / Au catalyst. Performed oxidative dehydrogenation in the presence of a gaseous mixture containing% by volume, 3-methyl-2-butenal is enriched and 3-methyl-2-butenol is depleted compared to the first product mixture. The second product mixture was obtained, where the molar ratio of 3-methyl-2-butenol to 3-methyl-2-butenal in the second product mixture was in the range of 75:25 to 35:65. And
Oxidative dehydrogenation in step ii) is further carried out in the presence of bases,
A method for preparing a composition containing 3-methyl-2-butenol and 3-methyl-2-butenal. The method of claim 1, wherein the catalyst used in step ii) is a Pd catalyst containing SiO ₂ and / or Al ₂ O ₃ as a carrier material. The method of claim 1 or 2, wherein the gas mixture used in step i) contains 3% to 10% by volume of oxygen. The method according to any one of claims 1 to 3, wherein the gas mixture used in step ii) contains 8% to 15% by volume of oxygen. The oxygen content of the gas mixture used in step i) is 2% to 10% by volume lower than the oxygen content of the gas mixture used in step ii), according to any one of claims 1 to 4. the method of. The first product mixture obtained in step i)
i.1 40% to 80% by weight 3-methyl-2-butenol,
i.20 0% to 15% by weight 3-methyl-2-butenal,
i.3 5% to 59% by weight 3-methyl-3-butenol, and
i.40 The method according to any one of claims 1 to 5, which comprises 0% to 10% by weight of a compound other than i.1, i.2, and i.3. The first product mixture obtained in step i)
i.1 45% to 70% by weight 3-methyl-2-butenol,
i.2 5% to 10% by weight 3-methyl-2-butenal,
i.3 20% to 50% by weight 3-methyl-3-butenol, as well as
i.40 The method according to any one of claims 1 to 6, which comprises 0% by weight to 5% by weight of a compound other than i.1, i.2, and i.3. The total proportion of 3-methyl-2-butenol, 3-methyl-2-butenal, and 3-methyl-3-butenol in the first product mixture obtained in step i) is the ratio of the first product mixture. The method according to any one of claims 1 to 7, which is at least 80% by weight based on the total weight. The method according to any one of claims 1 to 8, wherein step i) is performed without supplying an external solvent. From claim 1 where contact isomerization of 3-methyl-3-butenol in the presence of oxygen is performed with a conversion rate of 30% to 80% relative to the 3-methyl-3-butenol used. The method according to any one of 9. According to any one of claims 1 to 10, the product from the catalytic isomerization is used for oxidative dehydrogenation in step ii), optionally after removal of the catalyst, without further purification. The method described. 10. The proportion of bases in the reaction mixture is 0.01% to 2% by weight based on the total weight of the first product mixture used in step ii), according to any one of claims 1 to 11. the method of. The method according to any one of claims 1 to 12, wherein step ii) is performed without supplying an external solvent. In steps i) and ii), the oxygen-enriched gas mixture is continuously fed to the respective reaction regions and the oxygen-depleting gas mixture is continuously removed, where the oxygen-enriched gas mixture is the respective reaction mixture. The method according to any one of claims 1 to 13, which is supplied below the liquid surface of the above. The method according to any one of claims 1 to 14, which is carried out continuously. The second product mixture obtained in step ii) was subjected to distillation separation to obtain a product fraction enriched with 3-methyl-2-butenol and 3-methyl-2-butenal, and 3-methyl-3-. The method according to any one of claims 1 to 15, wherein the reaction fraction is enriched with butenol. 16. The method of claim 16, wherein the 3-methyl-3-butenol-enriched reactant fraction is used in step i), optionally with the addition of new 3-methyl-3-butenol.